The present invention relates to a clutch disc suitable for an automobile.
In a conventional type of friction clutch disc, an annular flange formed integrally with a spline hub has a plurarity of openings, recesses or the like, with which a first torsion spring (for a first torsion operation), second torsion springs and third torsion springs engage and through which stop pins protrude. Such openings and/or recesses are circumferentially adjacent to each other, thereby probably reducing the strength of the flange. Moreover, the first torsion spring is compressed throughout an entire torsion area of the clutch disc. In other words, the first torsion spring starts to be compressed before the second and the third springs are compressed, and the maximum compressed length of the first spring is longer and corresponds to a maximum torsion angle of the clutch disc. Therefore, the compression rate of the first spring is very rapid, and an intended first torsion operation (an operation in a small torsion area) is difficult to obtain with this type of first spring having rapid compression rate. Furthermore, the first spring is disposed at radially outer portion of the flange, the spring may not be sufficiently soft with respect to the torsion operation, even if a thin spring is used as the first spring. Further, according to the conventional structures, it is not easy to manufacture several types of the discs respectively having different hysteresis torque characteristics, which are attained by friction means such as annular friction washers.
In order to solve some of above-noted problems, the applicant has proposed structures in the U.S. patent application Ser. No. 347,157 filed in Feb. 9, 1982, now U.S. Pat. No. 4,494,642, in which a hub flange is divided into a radially outer flange and an inner flange. In this disc, a first spring is disposed between the inner and outer flanges, and the second (and third) springs are disposed in the outer flange. However, in this disc of the prior application, since the first spring, which is a compressible coil spring, is disposed at radially rather outer position, it may be impossible to sufficiently reduce the increasing rate of torque to be transmitted with respect to torsion angle. Further, the prior disc has also such disadvantages that it is hard to construct sufficiently compact structures and that the structures may be complicated.
Accordingly, it is an object of the invention to provide an improved disc, overcoming the above-noted disadvantages.
The essence of the present invention is provide a hub means divided into a radially outer hub and an inner hub connected by a first spring means disposed therebetween.
Other and further objects, features and advantages of the invention will appear more fully from the following description of the preferred embodiments of the invention.